On ebay you can sometimes find great deals on ex-display bikes that may have some aesthetic marks; fraction of the price for what is a new bike.

I got my first proper bike this way, it's a vitus cyclocross which I bought for it's versatility. It can be ridden fast on the road and has clearance and an appropriate geometry to put on wider tyres and tackle gravel/singletrack.

Decathlon do great bikes at good prices and their post-sale support is great. The triban 500 comes to mind first.